Reduced csi (channel state information)-rs (reference signal) density support for fd (full dimensional)-mimo (multiple input multiple output) systems

ABSTRACT

Techniques discussed herein can facilitate reduced density CSI (Channel State Information)-RS (Reference Signals). One example embodiment can be employed at a UE (User Equipment) and can comprise processing circuitry configured to receive and process a configuration message that comprises one or more configuration parameters for one or more CSI (Channel State Information)-RS (Reference Signal) APs (Antenna Ports) of a configurable density CSI-RS. The configuration parameters indicate a density of CSI-RS resource per Physical Resource Block (PRB) per CSI-RS AP and a PRB offset. The processing circuitry is further configured to determine a set of REs (Resource Elements) for the one or more CSI-RS APs of the configurable density CSI-RS based on the one or more configuration parameters and perform measurements on the configurable density CSI-RS from the set of REs to determine one or more CSI parameters. The one or more configuration parameters are provided per CSI-RS resource configuration.

REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of U.S. application Ser. No.16/467,566 filed on Jun. 7, 2019, which is a National Phase entryapplication of International Patent Application No. PCT/US2017/052194filed Sep. 19, 2017, which claims priority to U.S. ProvisionalApplication No. 62/397,695 filed Sep. 21, 2016, entitled “REDUCED CSI-RSDENSITY SUPPORT FOR FD-MIMO”, the contents of which are hereinincorporated by reference in their entirety.

FIELD

The present disclosure relates to wireless technology, and morespecifically to techniques for reducing CSI (Channel StateInformation)-RS (Reference Signal) density in FD (Full Dimensional)-MIMO(Multiple Input Multiple Output) systems.

BACKGROUND

The 3GPP (Third Generation Partnership Project) Rel-8 (Release 8) MIMO(Multiple Input Multiple Output) and subsequent MIMO enhancements inRel-10 and Rel-11 were designed to support antenna configurations at theeNodeB (Evolved Universal Terrestrial Radio Access Network (E-UTRAN)Node B) that are capable of adaptation in azimuth only. Recently, therehas been a significant interest in enhancing system performance throughthe use of antenna systems having a two-dimensional array structure thatprovides adaptive control over both the elevation dimension and theazimuth dimension. The additional control over the elevation dimensionenables a variety of strategies such as sector-specific elevationbeamforming (e.g., adaptive control over the vertical pattern beamwidthand/or downtilt), advanced sectorization in the vertical domain, anduser-specific elevation beamforming. Vertical sectorization can improveaverage system performance through the higher gain of the verticalsector patterns, but vertical sectorization generally does not needadditional standardization support. UE (User Equipment)-specificelevation beamforming promises to increase the SINR(Signal-to-Interference-plus-Noise Ratio) statistics seen by the UEs bypointing the vertical antenna pattern in the direction of the UE whilespraying less interference to adjacent sectors by virtue of being ableto steer the transmitted energy in elevation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating an example user equipment (UE)useable in connection with various aspects described herein.

FIG. 2 is a diagram illustrating example components of a device that canbe employed in accordance with various aspects discussed herein.

FIG. 3 is a diagram illustrating example interfaces of basebandcircuitry that can be employed in accordance with various aspectsdiscussed herein.

FIG. 4 is a block diagram illustrating a system employable at a UE (UserEquipment) that facilitates determination of CSI (Channel StateInformation) feedback based on reduced density CSI-RS (ReferenceSignal(s)), according to various aspects described herein.

FIG. 5 is a block diagram illustrating a system employable at a BS (BaseStation) that facilitates configuration for and transmission of reduceddensity CSI-RS to one or more UEs, according to various aspectsdescribed herein.

FIG. 6 is a diagram illustrating an example scenario implementingelevation beamforming in a FD-MIMO system, showing an example BS (e.g.,gNB, eNB, etc.) employing elevation beamforming to transmit to aplurality of UEs at different elevations, in connection with variousaspects described herein.

FIG. 7 is a diagram illustrating a physical resource block showingexample CSI (Channel State Information)-RS (Reference Signal) patternscorresponding to 2 CSI-RS antenna ports for normal cyclic prefix (CP),in connection with various aspects described herein.

FIG. 8 is a diagram illustrating a physical resource block showingexample CSI-RS patterns corresponding to 4 CSI-RS antenna ports fornormal CP, in connection with various aspects described herein.

FIG. 9 is a diagram illustrating a physical resource block showingexample CSI-RS patterns corresponding to 8 CSI-RS antenna ports fornormal CP, in connection with various aspects described herein.

FIG. 10 is a pair of diagrams illustrating example CSI-RS patterns withreduced density, according to various aspects described herein.

FIG. 11 is a pair of diagrams illustrating additional example CSI-RSpatterns with reduced density, according to various aspects describedherein.

FIG. 12 is a flow diagram of an example method employable at a UE thatfacilitates reception and measurement of reduced density CSI-RS,according to various aspects discussed herein.

FIG. 13 is a flow diagram of an example method employable at a BS thatfacilitates configuration for and transmission of reduced densityCSI-RS, according to various aspects discussed herein.

DETAILED DESCRIPTION

The present disclosure will now be described with reference to theattached drawing figures, wherein like reference numerals are used torefer to like elements throughout, and wherein the illustratedstructures and devices are not necessarily drawn to scale. As utilizedherein, terms “component,” “system,” “interface,” and the like areintended to refer to a computer-related entity, hardware, software(e.g., in execution), and/or firmware. For example, a component can be aprocessor (e.g., a microprocessor, a controller, or other processingdevice), a process running on a processor, a controller, an object, anexecutable, a program, a storage device, a computer, a tablet PC and/ora user equipment (e.g., mobile phone, etc.) with a processing device. Byway of illustration, an application running on a server and the servercan also be a component. One or more components can reside within aprocess, and a component can be localized on one computer and/ordistributed between two or more computers. A set of elements or a set ofother components can be described herein, in which the term “set” can beinterpreted as “one or more.”

Further, these components can execute from various computer readablestorage media having various data structures stored thereon such as witha module, for example. The components can communicate via local and/orremote processes such as in accordance with a signal having one or moredata packets (e.g., data from one component interacting with anothercomponent in a local system, distributed system, and/or across anetwork, such as, the Internet, a local area network, a wide areanetwork, or similar network with other systems via the signal).

As another example, a component can be an apparatus with specificfunctionality provided by mechanical parts operated by electric orelectronic circuitry, in which the electric or electronic circuitry canbe operated by a software application or a firmware application executedby one or more processors. The one or more processors can be internal orexternal to the apparatus and can execute at least a part of thesoftware or firmware application. As yet another example, a componentcan be an apparatus that provides specific functionality throughelectronic components without mechanical parts; the electroniccomponents can include one or more processors therein to executesoftware and/or firmware that confer(s), at least in part, thefunctionality of the electronic components.

Use of the word exemplary is intended to present concepts in a concretefashion. As used in this application, the term “or” is intended to meanan inclusive “or” rather than an exclusive “or”. That is, unlessspecified otherwise, or clear from context, “X employs A or B” isintended to mean any of the natural inclusive permutations. That is, ifX employs A; X employs B; or X employs both A and B, then “X employs Aor B” is satisfied under any of the foregoing instances. In addition,the articles “a” and “an” as used in this application and the appendedclaims should generally be construed to mean “one or more” unlessspecified otherwise or clear from context to be directed to a singularform. Furthermore, to the extent that the terms “including”, “includes”,“having”, “has”, “with”, or variants thereof are used in either thedetailed description and the claims, such terms are intended to beinclusive in a manner similar to the term “comprising.” Additionally, insituations wherein one or more numbered items are discussed (e.g., a“first X”, a “second X”, etc.), in general the one or more numbereditems may be distinct or they may be the same, although in somesituations the context may indicate that they are distinct or that theyare the same.

As used herein, the term “circuitry” may refer to, be part of, orinclude an Application Specific Integrated Circuit (ASIC), an electroniccircuit, a processor (shared, dedicated, or group), and/or memory(shared, dedicated, or group) that execute one or more software orfirmware programs, a combinational logic circuit, and/or other suitablehardware components that provide the described functionality. In someembodiments, the circuitry may be implemented in, or functionsassociated with the circuitry may be implemented by, one or moresoftware or firmware modules. In some embodiments, circuitry may includelogic, at least partially operable in hardware.

Embodiments described herein may be implemented into a system using anysuitably configured hardware and/or software. FIG. 1 illustrates anarchitecture of a system 100 of a network in accordance with someembodiments. The system 100 is shown to include a user equipment (UE)101 and a UE 102. The UEs 101 and 102 are illustrated as smartphones(e.g., handheld touchscreen mobile computing devices connectable to oneor more cellular networks), but may also comprise any mobile ornon-mobile computing device, such as Personal Data Assistants (PDAs),pagers, laptop computers, desktop computers, wireless handsets, or anycomputing device including a wireless communications interface.

In some embodiments, any of the UEs 101 and 102 can comprise an Internetof Things (IoT) UE, which can comprise a network access layer designedfor low-power IoT applications utilizing short-lived UE connections. AnIoT UE can utilize technologies such as machine-to-machine (M2M) ormachine-type communications (MTC) for exchanging data with an MTC serveror device via a public land mobile network (PLMN), Proximity-BasedService (ProSe) or device-to-device (D2D) communication, sensornetworks, or IoT networks. The M2M or MTC exchange of data may be amachine-initiated exchange of data. An IoT network describesinterconnecting IoT UEs, which may include uniquely identifiableembedded computing devices (within the Internet infrastructure), withshort-lived connections. The IoT UEs may execute background applications(e.g., keep-alive messages, status updates, etc.) to facilitate theconnections of the IoT network.

The UEs 101 and 102 may be configured to connect, e.g., communicativelycouple, with a radio access network (RAN) 110—the RAN 110 may be, forexample, an Evolved Universal Mobile Telecommunications System (UMTS)Terrestrial Radio Access Network (E-UTRAN), a NextGen RAN (NG RAN), orsome other type of RAN. The UEs 101 and 102 utilize connections 103 and104, respectively, each of which comprises a physical communicationsinterface or layer (discussed in further detail below); in this example,the connections 103 and 104 are illustrated as an air interface toenable communicative coupling, and can be consistent with cellularcommunications protocols, such as a Global System for MobileCommunications (GSM) protocol, a code-division multiple access (CDMA)network protocol, a Push-to-Talk (PTT) protocol, a PTT over Cellular(POC) protocol, a Universal Mobile Telecommunications System (UMTS)protocol, a 3GPP Long Term Evolution (LTE) protocol, a fifth generation(5G) protocol, a New Radio (NR) protocol, and the like.

In this embodiment, the UEs 101 and 102 may further directly exchangecommunication data via a ProSe interface 105. The ProSe interface 105may alternatively be referred to as a sidelink interface comprising oneor more logical channels, including but not limited to a PhysicalSidelink Control Channel (PSCCH), a Physical Sidelink Shared Channel(PSSCH), a Physical Sidelink Discovery Channel (PSDCH), and a PhysicalSidelink Broadcast Channel (PSBCH).

The UE 102 is shown to be configured to access an access point (AP) 106via connection 107. The connection 107 can comprise a local wirelessconnection, such as a connection consistent with any IEEE 802.11protocol, wherein the AP 106 would comprise a wireless fidelity (WiFi®)router. In this example, the AP 106 is shown to be connected to theInternet without connecting to the core network of the wireless system(described in further detail below).

The RAN 110 can include one or more access nodes that enable theconnections 103 and 104. These access nodes (ANs) can be referred to asbase stations (BSs), NodeBs, evolved NodeBs (eNBs), next GenerationNodeBs (gNB), RAN nodes, and so forth, and can comprise ground stations(e.g., terrestrial access points) or satellite stations providingcoverage within a geographic area (e.g., a cell). The RAN 110 mayinclude one or more RAN nodes for providing macrocells, e.g., macro RANnode 111, and one or more RAN nodes for providing femtocells orpicocells (e.g., cells having smaller coverage areas, smaller usercapacity, or higher bandwidth compared to macrocells), e.g., low power(LP) RAN node 112.

Any of the RAN nodes 111 and 112 can terminate the air interfaceprotocol and can be the first point of contact for the UEs 101 and 102.In some embodiments, any of the RAN nodes 111 and 112 can fulfillvarious logical functions for the RAN 110 including, but not limited to,radio network controller (RNC) functions such as radio bearermanagement, uplink and downlink dynamic radio resource management anddata packet scheduling, and mobility management.

In accordance with some embodiments, the UEs 101 and 102 can beconfigured to communicate using Orthogonal Frequency-DivisionMultiplexing (OFDM) communication signals with each other or with any ofthe RAN nodes 111 and 112 over a multicarrier communication channel inaccordance various communication techniques, such as, but not limitedto, an Orthogonal Frequency-Division Multiple Access (OFDMA)communication technique (e.g., for downlink communications) or a SingleCarrier Frequency Division Multiple Access (SC-FDMA) communicationtechnique (e.g., for uplink and ProSe or sidelink communications),although the scope of the embodiments is not limited in this respect.The OFDM signals can comprise a plurality of orthogonal subcarriers.

In some embodiments, a downlink resource grid can be used for downlinktransmissions from any of the RAN nodes 111 and 112 to the UEs 101 and102, while uplink transmissions can utilize similar techniques. The gridcan be a time-frequency grid, called a resource grid or time-frequencyresource grid, which is the physical resource in the downlink in eachslot. Such a time-frequency plane representation is a common practicefor OFDM systems, which makes it intuitive for radio resourceallocation. Each column and each row of the resource grid corresponds toone OFDM symbol and one OFDM subcarrier, respectively. The duration ofthe resource grid in the time domain corresponds to one slot in a radioframe. The smallest time-frequency unit in a resource grid is denoted asa resource element. Each resource grid comprises a number of resourceblocks, which describe the mapping of certain physical channels toresource elements. Each resource block comprises a collection ofresource elements; in the frequency domain, this may represent thesmallest quantity of resources that currently can be allocated. Thereare several different physical downlink channels that are conveyed usingsuch resource blocks.

The physical downlink shared channel (PDSCH) may carry user data andhigher-layer signaling to the UEs 101 and 102. The physical downlinkcontrol channel (PDCCH) may carry information about the transport formatand resource allocations related to the PDSCH channel, among otherthings. It may also inform the UEs 101 and 102 about the transportformat, resource allocation, and H-ARQ (Hybrid Automatic Repeat Request)information related to the uplink shared channel. Typically, downlinkscheduling (assigning control and shared channel resource blocks to theUE 102 within a cell) may be performed at any of the RAN nodes 111 and112 based on channel quality information fed back from any of the UEs101 and 102. The downlink resource assignment information may be sent onthe PDCCH used for (e.g., assigned to) each of the UEs 101 and 102.

The PDCCH may use control channel elements (CCEs) to convey the controlinformation. Before being mapped to resource elements, the PDCCHcomplex-valued symbols may first be organized into quadruplets, whichmay then be permuted using a sub-block interleaver for rate matching.Each PDCCH may be transmitted using one or more of these CCEs, whereeach CCE may correspond to nine sets of four physical resource elementsknown as resource element groups (REGs). Four Quadrature Phase ShiftKeying (QPSK) symbols may be mapped to each REG. The PDCCH can betransmitted using one or more CCEs, depending on the size of thedownlink control information (DCI) and the channel condition. There canbe four or more different PDCCH formats defined in LTE with differentnumbers of CCEs (e.g., aggregation level, L=1, 2, 4, or 8).

Some embodiments may use concepts for resource allocation for controlchannel information that are an extension of the above-describedconcepts. For example, some embodiments may utilize an enhanced physicaldownlink control channel (EPDCCH) that uses PDSCH resources for controlinformation transmission. The EPDCCH may be transmitted using one ormore enhanced the control channel elements (ECCEs). Similar to above,each ECCE may correspond to nine sets of four physical resource elementsknown as an enhanced resource element groups (EREGs). An ECCE may haveother numbers of EREGs in some situations.

The RAN 110 is shown to be communicatively coupled to a core network(CN) 120—via an S1 interface 113. In embodiments, the CN 120 may be anevolved packet core (EPC) network, a NextGen Packet Core (NPC) network,or some other type of CN. In this embodiment the S1 interface 113 issplit into two parts: the S1-U interface 114, which carries traffic databetween the RAN nodes 111 and 112 and the serving gateway (S-GW) 122,and the S1-mobility management entity (MME) interface 115, which is asignaling interface between the RAN nodes 111 and 112 and MMEs 121.

In this embodiment, the CN 120 comprises the MMEs 121, the S-GW 122, thePacket Data Network (PDN) Gateway (P-GW) 123, and a home subscriberserver (HSS) 124. The MMEs 121 may be similar in function to the controlplane of legacy Serving General Packet Radio Service (GPRS) SupportNodes (SGSN). The MMEs 121 may manage mobility aspects in access such asgateway selection and tracking area list management. The HSS 124 maycomprise a database for network users, including subscription-relatedinformation to support the network entities' handling of communicationsessions. The CN 120 may comprise one or several HSSs 124, depending onthe number of mobile subscribers, on the capacity of the equipment, onthe organization of the network, etc. For example, the HSS 124 canprovide support for routing/roaming, authentication, authorization,naming/addressing resolution, location dependencies, etc.

The S-GW 122 may terminate the S1 interface 113 towards the RAN 110, androutes data packets between the RAN 110 and the CN 120. In addition, theS-GW 122 may be a local mobility anchor point for inter-RAN nodehandovers and also may provide an anchor for inter-3GPP mobility. Otherresponsibilities may include lawful intercept, charging, and some policyenforcement.

The P-GW 123 may terminate an SGi interface toward a PDN. The P-GW 123may route data packets between the EPC network 123 and external networkssuch as a network including the application server 130 (alternativelyreferred to as application function (AF)) via an Internet Protocol (IP)interface 125. Generally, the application server 130 may be an elementoffering applications that use IP bearer resources with the core network(e.g., UMTS Packet Services (PS) domain, LTE PS data services, etc.). Inthis embodiment, the P-GW 123 is shown to be communicatively coupled toan application server 130 via an IP communications interface 125. Theapplication server 130 can also be configured to support one or morecommunication services (e.g., Voice-over-Internet Protocol (VoIP)sessions, PTT sessions, group communication sessions, social networkingservices, etc.) for the UEs 101 and 102 via the CN 120.

The P-GW 123 may further be a node for policy enforcement and chargingdata collection. Policy and Charging Enforcement Function (PCRF) 126 isthe policy and charging control element of the CN 120. In a non-roamingscenario, there may be a single PCRF in the Home Public Land MobileNetwork (HPLMN) associated with a UE's Internet Protocol ConnectivityAccess Network (IP-CAN) session. In a roaming scenario with localbreakout of traffic, there may be two PCRFs associated with a UE'sIP-CAN session: a Home PCRF (H-PCRF) within a HPLMN and a Visited PCRF(V-PCRF) within a Visited Public Land Mobile Network (VPLMN). The PCRF126 may be communicatively coupled to the application server 130 via theP-GW 123. The application server 130 may signal the PCRF 126 to indicatea new service flow and select the appropriate Quality of Service (QoS)and charging parameters. The PCRF 126 may provision this rule into aPolicy and Charging Enforcement Function (PCEF) (not shown) with theappropriate traffic flow template (TFT) and QoS class of identifier(QCI), which commences the QoS and charging as specified by theapplication server 130.

FIG. 2 illustrates example components of a device 200 in accordance withsome embodiments. In some embodiments, the device 200 may includeapplication circuitry 202, baseband circuitry 204, Radio Frequency (RF)circuitry 206, front-end module (FEM) circuitry 208, one or moreantennas 210, and power management circuitry (PMC) 212 coupled togetherat least as shown. The components of the illustrated device 200 may beincluded in a UE or a RAN node. In some embodiments, the device 200 mayinclude less elements (e.g., a RAN node may not utilize applicationcircuitry 202, and instead include a processor/controller to process IPdata received from an EPC). In some embodiments, the device 200 mayinclude additional elements such as, for example, memory/storage,display, camera, sensor, or input/output (I/O) interface. In otherembodiments, the components described below may be included in more thanone device (e.g., said circuitries may be separately included in morethan one device for Cloud-RAN (C-RAN) implementations).

The application circuitry 202 may include one or more applicationprocessors. For example, the application circuitry 202 may includecircuitry such as, but not limited to, one or more single-core ormulti-core processors. The processor(s) may include any combination ofgeneral-purpose processors and dedicated processors (e.g., graphicsprocessors, application processors, etc.). The processors may be coupledwith or may include memory/storage and may be configured to executeinstructions stored in the memory/storage to enable various applicationsor operating systems to run on the device 200. In some embodiments,processors of application circuitry 202 may process IP data packetsreceived from an EPC.

The baseband circuitry 204 may include circuitry such as, but notlimited to, one or more single-core or multi-core processors. Thebaseband circuitry 204 may include one or more baseband processors orcontrol logic to process baseband signals received from a receive signalpath of the RF circuitry 206 and to generate baseband signals for atransmit signal path of the RF circuitry 206. Baseband circuitry 204 mayinterface with the application circuitry 202 for generation andprocessing of the baseband signals and for controlling operations of theRF circuitry 206. For example, in some embodiments, the basebandcircuitry 204 may include a third generation (3G) baseband processor204A, a fourth generation (4G) baseband processor 204B, a fifthgeneration (5G) baseband processor 204C, or other baseband processor(s)204D for other existing generations, generations in development or to bedeveloped in the future (e.g., second generation (2G), sixth generation(6G), etc.). The baseband circuitry 204 (e.g., one or more of basebandprocessors 204A-D) may handle various radio control functions thatenable communication with one or more radio networks via the RFcircuitry 206. In other embodiments, some or all of the functionality ofbaseband processors 204A-D may be included in modules stored in thememory 204G and executed via a Central Processing Unit (CPU) 204E. Theradio control functions may include, but are not limited to, signalmodulation/demodulation, encoding/decoding, radio frequency shifting,etc. In some embodiments, modulation/demodulation circuitry of thebaseband circuitry 204 may include Fast-Fourier Transform (FFT),precoding, or constellation mapping/demapping functionality. In someembodiments, encoding/decoding circuitry of the baseband circuitry 204may include convolution, tailbiting convolution, turbo, Viterbi, or LowDensity Parity Check (LDPC) encoder/decoder functionality. Embodimentsof modulation/demodulation and encoder/decoder functionality are notlimited to these examples and may include other suitable functionalityin other embodiments.

In some embodiments, the baseband circuitry 204 may include one or moreaudio digital signal processor(s) (DSP) 204F. The audio DSP(s) 204F maybe include elements for compression/decompression and echo cancellationand may include other suitable processing elements in other embodiments.Components of the baseband circuitry may be suitably combined in asingle chip, a single chipset, or disposed on a same circuit board insome embodiments. In some embodiments, some or all of the constituentcomponents of the baseband circuitry 204 and the application circuitry202 may be implemented together such as, for example, on a system on achip (SOC).

In some embodiments, the baseband circuitry 204 may provide forcommunication compatible with one or more radio technologies. Forexample, in some embodiments, the baseband circuitry 204 may supportcommunication with an evolved universal terrestrial radio access network(EUTRAN) or other wireless metropolitan area networks (WMAN), a wirelesslocal area network (WLAN), a wireless personal area network (WPAN).Embodiments in which the baseband circuitry 204 is configured to supportradio communications of more than one wireless protocol may be referredto as multi-mode baseband circuitry.

RF circuitry 206 may enable communication with wireless networks usingmodulated electromagnetic radiation through a non-solid medium. Invarious embodiments, the RF circuitry 206 may include switches, filters,amplifiers, etc. to facilitate the communication with the wirelessnetwork. RF circuitry 206 may include a receive signal path which mayinclude circuitry to down-convert RF signals received from the FEMcircuitry 208 and provide baseband signals to the baseband circuitry204. RF circuitry 206 may also include a transmit signal path which mayinclude circuitry to up-convert baseband signals provided by thebaseband circuitry 204 and provide RF output signals to the FEMcircuitry 208 for transmission.

In some embodiments, the receive signal path of the RF circuitry 206 mayinclude mixer circuitry 206 a, amplifier circuitry 206 b and filtercircuitry 206 c. In some embodiments, the transmit signal path of the RFcircuitry 206 may include filter circuitry 206 c and mixer circuitry 206a. RF circuitry 206 may also include synthesizer circuitry 206 d forsynthesizing a frequency for use by the mixer circuitry 206 a of thereceive signal path and the transmit signal path. In some embodiments,the mixer circuitry 206 a of the receive signal path may be configuredto down-convert RF signals received from the FEM circuitry 208 based onthe synthesized frequency provided by synthesizer circuitry 206 d. Theamplifier circuitry 206 b may be configured to amplify thedown-converted signals and the filter circuitry 206 c may be a low-passfilter (LPF) or band-pass filter (BPF) configured to remove unwantedsignals from the down-converted signals to generate output basebandsignals. Output baseband signals may be provided to the basebandcircuitry 204 for further processing. In some embodiments, the outputbaseband signals may be zero-frequency baseband signals, although thisis not a requirement. In some embodiments, mixer circuitry 206 a of thereceive signal path may comprise passive mixers, although the scope ofthe embodiments is not limited in this respect.

In some embodiments, the mixer circuitry 206 a of the transmit signalpath may be configured to up-convert input baseband signals based on thesynthesized frequency provided by the synthesizer circuitry 206 d togenerate RF output signals for the FEM circuitry 208. The basebandsignals may be provided by the baseband circuitry 204 and may befiltered by filter circuitry 206 c.

In some embodiments, the mixer circuitry 206 a of the receive signalpath and the mixer circuitry 206 a of the transmit signal path mayinclude two or more mixers and may be arranged for quadraturedownconversion and upconversion, respectively. In some embodiments, themixer circuitry 206 a of the receive signal path and the mixer circuitry206 a of the transmit signal path may include two or more mixers and maybe arranged for image rejection (e.g., Hartley image rejection). In someembodiments, the mixer circuitry 206 a of the receive signal path andthe mixer circuitry 206 a may be arranged for direct downconversion anddirect upconversion, respectively. In some embodiments, the mixercircuitry 206 a of the receive signal path and the mixer circuitry 206 aof the transmit signal path may be configured for super-heterodyneoperation.

In some embodiments, the output baseband signals and the input basebandsignals may be analog baseband signals, although the scope of theembodiments is not limited in this respect. In some alternateembodiments, the output baseband signals and the input baseband signalsmay be digital baseband signals. In these alternate embodiments, the RFcircuitry 206 may include analog-to-digital converter (ADC) anddigital-to-analog converter (DAC) circuitry and the baseband circuitry204 may include a digital baseband interface to communicate with the RFcircuitry 206.

In some dual-mode embodiments, a separate radio IC circuitry may beprovided for processing signals for each spectrum, although the scope ofthe embodiments is not limited in this respect.

In some embodiments, the synthesizer circuitry 206 d may be afractional-N synthesizer or a fractional N/N+1 synthesizer, although thescope of the embodiments is not limited in this respect as other typesof frequency synthesizers may be suitable. For example, synthesizercircuitry 206 d may be a delta-sigma synthesizer, a frequencymultiplier, or a synthesizer comprising a phase-locked loop with afrequency divider.

The synthesizer circuitry 206 d may be configured to synthesize anoutput frequency for use by the mixer circuitry 206 a of the RFcircuitry 206 based on a frequency input and a divider control input. Insome embodiments, the synthesizer circuitry 206 d may be a fractionalN/N+1 synthesizer.

In some embodiments, frequency input may be provided by a voltagecontrolled oscillator (VCO), although that is not a requirement. Dividercontrol input may be provided by either the baseband circuitry 204 orthe applications circuitry 202 depending on the desired outputfrequency. In some embodiments, a divider control input (e.g., N) may bedetermined from a look-up table based on a channel indicated by theapplications circuitry 202.

Synthesizer circuitry 206 d of the RF circuitry 206 may include adivider, a delay-locked loop (DLL), a multiplexer and a phaseaccumulator. In some embodiments, the divider may be a dual modulusdivider (DMD) and the phase accumulator may be a digital phaseaccumulator (DPA). In some embodiments, the DMD may be configured todivide the input signal by either N or N+1 (e.g., based on a carry out)to provide a fractional division ratio. In some example embodiments, theDLL may include a set of cascaded, tunable, delay elements, a phasedetector, a charge pump and a D-type flip-flop. In these embodiments,the delay elements may be configured to break a VCO period up into Ndequal packets of phase, where Nd is the number of delay elements in thedelay line. In this way, the DLL provides negative feedback to helpensure that the total delay through the delay line is one VCO cycle.

In some embodiments, synthesizer circuitry 206 d may be configured togenerate a carrier frequency as the output frequency, while in otherembodiments, the output frequency may be a multiple of the carrierfrequency (e.g., twice the carrier frequency, four times the carrierfrequency) and used in conjunction with quadrature generator and dividercircuitry to generate multiple signals at the carrier frequency withmultiple different phases with respect to each other. In someembodiments, the output frequency may be a LO frequency (fLO). In someembodiments, the RF circuitry 206 may include an IQ/polar converter.

FEM circuitry 208 may include a receive signal path which may includecircuitry configured to operate on RF signals received from one or moreantennas 210, amplify the received signals and provide the amplifiedversions of the received signals to the RF circuitry 206 for furtherprocessing. FEM circuitry 208 may also include a transmit signal pathwhich may include circuitry configured to amplify signals fortransmission provided by the RF circuitry 206 for transmission by one ormore of the one or more antennas 210. In various embodiments, theamplification through the transmit or receive signal paths may be donesolely in the RF circuitry 206, solely in the FEM 208, or in both the RFcircuitry 206 and the FEM 208.

In some embodiments, the FEM circuitry 208 may include a TX/RX switch toswitch between transmit mode and receive mode operation. The FEMcircuitry may include a receive signal path and a transmit signal path.The receive signal path of the FEM circuitry may include an LNA toamplify received RF signals and provide the amplified received RFsignals as an output (e.g., to the RF circuitry 206). The transmitsignal path of the FEM circuitry 208 may include a power amplifier (PA)to amplify input RF signals (e.g., provided by RF circuitry 206), andone or more filters to generate RF signals for subsequent transmission(e.g., by one or more of the one or more antennas 210).

In some embodiments, the PMC 212 may manage power provided to thebaseband circuitry 204. In particular, the PMC 212 may controlpower-source selection, voltage scaling, battery charging, or DC-to-DCconversion. The PMC 212 may often be included when the device 200 iscapable of being powered by a battery, for example, when the device isincluded in a UE. The PMC 212 may increase the power conversionefficiency while providing desirable implementation size and heatdissipation characteristics.

While FIG. 2 shows the PMC 212 coupled only with the baseband circuitry204. However, in other embodiments, the PMC 212 may be additionally oralternatively coupled with, and perform similar power managementoperations for, other components such as, but not limited to,application circuitry 202, RF circuitry 206, or FEM 208.

In some embodiments, the PMC 212 may control, or otherwise be part of,various power saving mechanisms of the device 200. For example, if thedevice 200 is in an RRC_Connected state, where it is still connected tothe RAN node as it expects to receive traffic shortly, then it may entera state known as Discontinuous Reception Mode (DRX) after a period ofinactivity. During this state, the device 200 may power down for briefintervals of time and thus save power.

If there is no data traffic activity for an extended period of time,then the device 200 may transition off to an RRC_Idle state, where itdisconnects from the network and does not perform operations such aschannel quality feedback, handover, etc. The device 200 goes into a verylow power state and it performs paging where again it periodically wakesup to listen to the network and then powers down again. The device 200may not receive data in this state, in order to receive data, it musttransition back to RRC_Connected state.

An additional power saving mode may allow a device to be unavailable tothe network for periods longer than a paging interval (ranging fromseconds to a few hours). During this time, the device is totallyunreachable to the network and may power down completely. Any data sentduring this time incurs a large delay and it is assumed the delay isacceptable.

Processors of the application circuitry 202 and processors of thebaseband circuitry 204 may be used to execute elements of one or moreinstances of a protocol stack. For example, processors of the basebandcircuitry 204, alone or in combination, may be used execute Layer 3,Layer 2, or Layer 1 functionality, while processors of the applicationcircuitry 202 may utilize data (e.g., packet data) received from theselayers and further execute Layer 4 functionality (e.g., transmissioncommunication protocol (TCP) and user datagram protocol (UDP) layers).As referred to herein, Layer 3 may comprise a radio resource control(RRC) layer, described in further detail below. As referred to herein,Layer 2 may comprise a medium access control (MAC) layer, a radio linkcontrol (RLC) layer, and a packet data convergence protocol (PDCP)layer, described in further detail below. As referred to herein, Layer 1may comprise a physical (PHY) layer of a UE/RAN node, described infurther detail below.

FIG. 3 illustrates example interfaces of baseband circuitry inaccordance with some embodiments. As discussed above, the basebandcircuitry 204 of FIG. 2 may comprise processors 204A-204E and a memory204G utilized by said processors. Each of the processors 204A-204E mayinclude a memory interface, 304A-304E, respectively, to send/receivedata to/from the memory 204G.

The baseband circuitry 204 may further include one or more interfaces tocommunicatively couple to other circuitries/devices, such as a memoryinterface 312 (e.g., an interface to send/receive data to/from memoryexternal to the baseband circuitry 204), an application circuitryinterface 314 (e.g., an interface to send/receive data to/from theapplication circuitry 202 of FIG. 2), an RF circuitry interface 316(e.g., an interface to send/receive data to/from RF circuitry 206 ofFIG. 2), a wireless hardware connectivity interface 318 (e.g., aninterface to send/receive data to/from Near Field Communication (NFC)components, Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi®components, and other communication components), and a power managementinterface 320 (e.g., an interface to send/receive power or controlsignals to/from the PMC 212).

Referring to FIG. 4, illustrated is a block diagram of a system 400employable at a UE (User Equipment) that facilitates determination ofCSI (Channel State Information) feedback based on reduced densityCSI-RS, according to various aspects described herein. System 400 caninclude one or more processors 410 (e.g., one or more basebandprocessors such as one or more of the baseband processors discussed inconnection with FIG. 2 and/or FIG. 3) comprising processing circuitryand associated memory interface(s) (e.g., memory interface(s) discussedin connection with FIG. 3), transceiver circuitry 420 (e.g., comprisingone or more of transmitter circuitry or receiver circuitry, which canemploy common circuit elements, distinct circuit elements, or acombination thereof), and a memory 430 (which can comprise any of avariety of storage mediums and can store instructions and/or dataassociated with one or more of processor(s) 410 or transceiver circuitry420). In various aspects, system 400 can be included within a userequipment (UE). As described in greater detail below, system 400 canfacilitate configuration of the UE to receive reduced density CSI-RS,and subsequent CSI feedback.

In various aspects discussed herein, signals and/or messages can begenerated and output for transmission, and/or transmitted messages canbe received and processed. Depending on the type of signal or messagegenerated, outputting for transmission (e.g., by processor(s) 410,processor(s) 510, etc.) can comprise one or more of the following:generating a set of associated bits that indicate the content of thesignal or message, coding (e.g., which can include adding a cyclicredundancy check (CRC) and/or coding via one or more of turbo code, lowdensity parity-check (LDPC) code, tailbiting convolution code (TBCC),etc.), scrambling (e.g., based on a scrambling seed), modulating (e.g.,via one of binary phase shift keying (BPSK), quadrature phase shiftkeying (QPSK), or some form of quadrature amplitude modulation (QAM),etc.), and/or resource mapping (e.g., to a scheduled set of resources,to a set of time and frequency resources granted for uplinktransmission, etc.). Depending on the type of received signal ormessage, processing (e.g., by processor(s) 410, processor(s) 510, etc.)can comprise one or more of: identifying physical resources associatedwith the signal/message, detecting the signal/message, resource elementgroup deinterleaving, demodulation, descrambling, and/or decoding.

Referring to FIG. 5, illustrated is a block diagram of a system 500employable at a BS (Base Station) that facilitates configuration for andtransmission of reduced density CSI-RS to one or more UEs, according tovarious aspects described herein. System 500 can include one or moreprocessors 510 (e.g., one or more baseband processors such as one ormore of the baseband processors discussed in connection with FIG. 2and/or FIG. 3) comprising processing circuitry and associated memoryinterface(s) (e.g., memory interface(s) discussed in connection withFIG. 3), communication circuitry 520 (e.g., which can comprise circuitryfor one or more wired (e.g., X2, etc.) connections and/or transceivercircuitry that can comprise one or more of transmitter circuitry (e.g.,associated with one or more transmit chains) or receiver circuitry(e.g., associated with one or more receive chains), wherein thetransmitter circuitry and receiver circuitry can employ common circuitelements, distinct circuit elements, or a combination thereof), andmemory 530 (which can comprise any of a variety of storage mediums andcan store instructions and/or data associated with one or more ofprocessor(s) 510 or communication circuitry 520). In various aspects,system 500 can be included within an Evolved Universal Terrestrial RadioAccess Network (E-UTRAN) Node B (Evolved Node B, eNodeB, or eNB), nextgeneration Node B (gNodeB or gNB) or other base station in a wirelesscommunications network. In some aspects, the processor(s) 510,communication circuitry 520, and the memory 530 can be included in asingle device, while in other aspects, they can be included in differentdevices, such as part of a distributed architecture. As described ingreater detail below, system 500 can facilitate configuration of one ormore UEs for reduced density CSI-RS.

Referring to FIG. 6, illustrated is a diagram of an example scenarioimplementing elevation beamforming in a FD-MIMO system, showing anexample BS (e.g., gNB, eNB, etc.) 610 employing elevation beamforming totransmit to a plurality of UEs 620 at different elevations, inconnection with various aspects described herein.

In Rel-13 FD (Full Dimensional)-MIMO, two types of CSI (Channel StateInformation) feedback schemes were specified to support FD-MIMO—class A(also known as CSI for non-precoded CSI-RS (Reference Signal)) and classB (also known as CSI for beamformed CSI-RS). In the class A scheme,CSI-RS is transmitted from each physical antenna of the eNB withoutadditional beamforming, while in class B, the CSI-RS antenna ports arebeamformed prior to transmission from the physical antennas. Due to thebeamforming gain, CSI reporting for class B can be advantageous,especially in coverage limited scenarios (e.g., higher frequency banddeployment scenarios).

The cell-edge performance for SU (Single User)-MIMO and cell-centerperformance for MU (Multi User)-MIMO can be improved by using highresolution feedback. For class B CSI reporting, high resolution feedbackcan be achieved by transmitting additional CSI-RS resources (K>1) orports (K=1), which can be associated with the additional beams. Forexample, the additional beams can be obtained by ‘x’ times beamoversampling, which involves ‘x’ times more CSI-RS resources or portscomparing to CSI reporting without beam oversampling. However, theseadditional CSI-RS resources or ports increase overhead involved inCSI-RS, and impact system performance. In various aspects, techniquesdiscussed herein can be employed to reduce overhead due to CSI-RS, whichcan minimize the impact on system performance due to of the additionalCSI-RS resource(s) or port(s).

In Rel-13 (3GPP Release 13), CSI-RS for class B relies on the legacystructure of CSI-RS defined in LTE (Long Term Evolution)-A (Advanced)for Rel-10. The legacy CSI-RS supports 1, 2, 4 or 8 antenna ports. Thedensity of conventional CSI-RS (e.g., generated by processor(s) 510,transmitted via communication circuitry 520, received via transceivercircuitry 420, and processed by processor(s) 410) is 1 resource elementper PRB (Physical Resource Block) per CSI-RS antenna port. ConventionalCSI-RS can be located in every PRB pair and periodically transmittedwith a minimum periodicity of 5 ms. The CSI-RS structure for differentnumbers of antenna ports can have a nested structure, such that theCSI-RS resources corresponding to a lower number of antenna ports can bea subset of the CSI-RS resource of a CSI-RS pattern corresponding tohigher number of CSI-RS antenna ports. The parameters of CSI-RS can beconfigured to the UE using DCI (Downlink Control Information) and/orhigher layer signaling (e.g., RRC (Radio Resource Control) messaginggenerated by processor(s) 510, transmitted via communication circuitry520, received via transceiver circuitry 420, and processed byprocessor(s) 410).

Referring to FIG. 7, illustrated is a diagram of a physical resourceblock showing example CSI-RS patterns (labeled A-T) corresponding to 2CSI-RS ports are shown for normal cyclic prefix (CP), where ports 0-1(e.g., A0-A1, B0-B1, etc.) correspond to CSI-RS ports 15-16,respectively, in connection with various aspects described herein.Referring to FIG. 8, illustrated is a diagram of a physical resourceblock showing example CSI-RS patterns (labeled A-J) corresponding to 4CSI-RS ports are shown for normal CP, where ports 0-3 (e.g., A0-A3,B0-B3, etc.) correspond to CSI-RS ports 15-18, respectively inconnection with various aspects described herein. Referring to FIG. 9,illustrated is a diagram of a physical resource block showing exampleCSI-RS patterns (labeled A-E) corresponding to 8 CSI-RS ports are shownfor normal CP, where ports 0-7 (e.g., A0-A7, B0-B7, etc.) correspond toCSI-RS ports 15-22, respectively, in connection with various aspectsdescribed herein.

In various aspects, techniques and associated control signaling arediscussed herein that can facilitate CSI-RS having a reduced density.These techniques can include: (a) Separate and/or joint coding of PRBdecimation and PRB offset for indication (e.g., via DCI and/or higherlayer signaling generated by processor(s) 510, transmitted viacommunication circuitry 520, received via transceiver circuitry 420, andprocessed by processor(s) 410) of the reduced density CSI-RStransmission, (b) PDSCH (Physical Downlink Shared Channel) RE (ResourceElement) mapping determination based on the non-reduced density of NZP(Non-Zero Power) CSI-RS, (c) Collision handling of NZP CSI-RS withbroadcast channels (e.g., including channels with system and paginginformation) based on non-reduced density of NZP CSI-RS, and (d) Antennaport renumbering for localized beam transmission on NZP CSI-RS REs.

In various aspects, a PRB decimation (e.g., which can indicate a densityof reduced density CSI-RS, for example, of 1 resource element per N PRBsper CSI-RS antenna port, where N is the PRB decimation) and a PRB offset(which can indicate an offset in terms of a number of PRBs and/orportions thereof (e.g., subcarriers) for some or all of CSI-RS APsrelative to the CSI-RS configuration) can be employed to indicate theREs employed for transmission (e.g., by communication circuitry 520) ofreduced density CSI-RS (e.g., generated by processor(s) 510). In variousaspects, the PRB decimation and/or the PRB offset can be indicated by aBS (e.g., gNB, eNB, etc.) to the UE using two independent parameterssuch as PRB decimation and PRB offset (e.g., via DCI (Downlink ControlInformation) and/or higher layer signaling generated by processor(s)510, transmitted via communication circuitry 520, received viatransceiver circuitry 420, and processed by processor(s) 410). In somesuch aspects, the PRB decimation and the PRB offset can be separatelyindicated (e.g., in the same or different DCI or higher layer signaling,etc.).

In various aspects, to reduce control signaling (e.g., for DCI basedindication, etc.), joint coding of the PRB decimation and the PRB offsetcan be employed (e.g., via DCI and/or higher layer signaling generatedby processor(s) 510, transmitted via communication circuitry 520,received via transceiver circuitry 420, and processed by processor(s)410). For joint coding aspects, a single parameter (e.g., a CSI-RSdensity configuration index) can be indicated, where each value of thatparameter can correspond to a distinct combination of values of the PRBdecimation and the PRB offset. One example of joint coding of the PRBdecimation and PRB offset for reduced density CSI-RS is provided inTable 1, below, where CSI-RS density configuration index indicates boththe PRB decimation and the PRB offset for CSI-RS REs. The rows in Table1 corresponding to PRB decimation value of X contains PRB offsets 0, . .. , X−1, where X is the density of CSI-RS antenna port transmission, thenumber of PRBs per antenna port.

TABLE 1 Example joint coding of PRB decimation and PRB offset CSI-RSdensity PRB decimation for CSI- PRB offset for CSI- configuration indexRS REs (PRBs) RS REs (PRBs) 0 0 0 1 2 0 2 2 1 3 4 0 4 4 1 5 4 2 6 4 3

In various embodiments, the PRB decimation and the PRB offset can beseparately indicated, or can be jointly indicated as in Table 1 orsimilarly, based on a single parameter (e.g., CSI-RS densityconfiguration index, etc.) with values that each correspond to adistinct pair of a PRB decimation (e.g., in PRBs) and a PRB offset(e.g., in PRBs and/or subcarriers).

In various aspects, a PRB decimation and a PRB offset can be provided orconfigured (e.g., via DCI and/or higher layer signaling generated byprocessor(s) 510, transmitted via communication circuitry 520, receivedvia transceiver circuitry 420, and processed by processor(s) 410): (a)per CSI-RS AP (antenna port), wherein the number of parameters (forjoint indication) or parameter sets (for separate indication) of thereduced density CSI-RS corresponds to the number of CSI-RS APs; (b) pergroup of CSI-RS APs, wherein the number of parameters (for jointindication) or parameter sets (for separate indication) of the reduceddensity CSI-RS corresponds to the number of CSI-RS AP groups; (c) perCSI-RS resource configuration, wherein the number of parameters (forjoint indication) or parameter sets (for separate indication) of thereduced density CSI-RS corresponds to the number of CSI-RS resourceconfigurations per NZP CSI-RS resource; or (d) per NZP CSI-RS resourcecomprising aggregation of one or more CSI-RS resource configurations.

In various aspects, the parameters of reduced density CSI-RS (e.g., PRBdecimation and PRB offset, either separately or jointly indicated) canbe indicated using DCI and/or RRC (e.g., generated by processor(s) 510,transmitted via communication circuitry 520, received via transceivercircuitry 420, and processed by processor(s) 410). In some aspects(e.g., employing separate indication of PRB decimation and PRB offset,etc.), a combination of RRC and DCI (e.g., generated by processor(s)510, transmitted via communication circuitry 520, received viatransceiver circuitry 420, and processed by processor(s) 410) can beemployed to indicate the parameters of reduced density CSI-RS. In oneexample, the PRB decimation (density of port CSI-RS REs) can beconfigured via RRC (e.g., generated by processor(s) 510, transmitted viacommunication circuitry 520, received via transceiver circuitry 420, andprocessed by processor(s) 410) and the PRB offset can be provided usingDCI (e.g., generated by processor(s) 510, transmitted via communicationcircuitry 520, received via transceiver circuitry 420, and processed byprocessor(s) 410).

In various aspects, the collision handling of reduced density CSI-RS(e.g., with ZP or other NZP CSI-RS resource, paging messages (e.g. inthe primary cell in subframes/slots configured for transmission ofpaging messages in the primary cell for any UE with the cell-specificpaging configuration), broadcast messages (e.g. transmitted SIBs (e.g.,SystemInformationBlockType1, etc.)), etc.) can be managed based onassuming non-reduced density (e.g., conventional) CSI-RS, where theCSI-RS antenna ports can be assumed as transmitted on each PRBregardless of the actual CSI-RS density configuration.

In various aspects, mapping (e.g., by processor(s) 510) of PDSCH(Physical Downlink Shared Channel) REs (Resource Elements) can be alsodetermined (e.g., by processor(s) assuming non-reduced density CSI-RS(e.g., where each CSI-RS AP is transmitted in every PRB), regardless ofthe actual CSI-RS density configuration.

In various aspects, groups of CSI-RS antenna ports (e.g., generated byprocessor(s) 510) can be transmitted (e.g., via communication circuitry520) with the same PRB offset or with different PRB offsets. Referringto FIG. 10, illustrated is a diagram showing two examples of reduceddensity CSI-RS wherein groups of CSI-RS antenna ports are transmittedwith different PRB offsets, according to various aspects discussedherein. Referring to FIG. 11, illustrated is a diagram showing twoexamples of reduced density CSI-RS, with the left example having groupsof CSI-RS antenna ports transmitted with the same PRB offsets and theright example having groups of CSI-RS antenna ports transmitted withdifferent PRB offsets, according to various aspects discussed herein. Inboth examples of FIG. 10, the antenna ports corresponding to the firstgroup containing antenna ports {19,20,21,22} (e.g., as generated byprocessor(s) 510) can be transmitted (e.g., by communication circuitry520) with one PRB offset on even PRBs, while the second group of antennaports {15,16,17,18} (e.g., as generated by processor(s) 510) can betransmitted (e.g., by communication circuitry 520) with another PRBoffset on odd PRBs. For example, the left example of FIG. 10 can have aPRB offset of 11 subcarriers for APs {15,16,17,18} and 0 subcarriers forAPs {19,20,21,22}, while the right example of FIG. 10 can have a PRBoffset of 0 subcarriers for APs {15,16,17,18} and 13 subcarriers for APs{19,20,21,22}. In the left example of FIG. 11, the same PRB offset canbe applied (e.g., by processor(s) 510 and communication circuitry 520)for all APs, while in the right example, a different PRB offset can beapplied (e.g., by processor(s) 510 and communication circuitry 520) foreach pair of APs {15,16}, {17,18}, {19,20}, and {21,22}.

In various aspects, as in each of the examples of FIGS. 10 and 11, PRBoffset(s) can be applied (e.g., by processor(s) 510 and communicationcircuitry 520) to groups of CSI-RS APs such that the occupied REs (inoccupied PRBs) corresponded to a predefined CSI-RS pattern as shown inFIG. 7, 8, or 9. In other aspects, other PRB offsets can be applied.

Due to the current structure of CSI-RS, the antenna ports in the{15,16,17,18} group can correspond to a first polarization (e.g.,horizontal or vertical) of four different beams, and the APs in the{19,20,21,22} can correspond to a second polarization (e.g., vertical orhorizontal) of the same beams. As a result, in scenarios with mappingsof APs {15,16,17,18} and {19,20,21,22} to different PRBs, the antennaports corresponding to the same beam but different polarizations canexperience different phase drifts that might be difficult to compensateusing PMIs (Precoding Matrix Indicators). In various aspects, to solvethe phase drifting issue, antenna port renumbering can be applied (e.g.,by processor(s) 410 and/or processor(s) 510) prior to CSI calculation.The renumbering of antenna ports can ensure that the same beamcorresponding to different polarizations can be transmitted (e.g., bycommunication circuitry 520) on the same pair of REs (e.g., as mapped byprocessor(s) 510). Equation (1), below, provides an example equation forCSI-RS AP renumbering according to various aspects discussed herein:

$\begin{matrix}{p = \left\{ \begin{matrix}{{15} + i} & {{{for}\ p^{\prime}} \in \left\{ {15,\ldots,{15 + {2i}}} \right\}} \\{{15} + i + \frac{N_{ports}^{CSI}}{2}} & {{{for}p^{\prime}} \in \left\{ {16,\ldots,{15 + {2i} + 1}} \right\}}\end{matrix} \right.} & (1)\end{matrix}$${i = \left\{ {0,1,\ldots,{\frac{N_{ports}^{CSI}}{2} - 1}} \right\}},$

where p′ is the antenna port before renumbering (used for channelmeasurements, e.g., by processor(s) 410), p is the antenna port afterrenumbering (to be used for CSI calculation, e.g., by processor(s) 410),N_(ports) ^(CSI) corresponds to the number of CSI-RS antenna ports (andcan be, e.g., 2, 4 or 8, etc.). However, such aspects can be extendedbeyond conventional numbers of CSI-RS antenna ports. An example ofrenumbering is for 8 port case is provided below.

In an example of CSI-RS antenna port renumbering for an 8 CSI-RS antennaport case, CSI-RS APs {15,17,19,21} for measurements can correspond toCSI-RS APs {15,16,17,18} for CSI feedback, and CSI-RS APs {16,18,20,22}for measurements can correspond to CSI-RS APs {19,20,21,22} for CSIfeedback.

Referring to FIG. 12, illustrated is a flow diagram of an example method1200 employable at a UE that facilitates reception and measurement ofreduced density CSI-RS, according to various aspects discussed herein.In other aspects, a machine readable medium can store instructionsassociated with method 1200 that, when executed, can cause a UE toperform the acts of method 1200.

At 1210, one or more configuration messages can be received that canindicate one or more configuration parameters for reduced density CSI-RS(e.g., PRB decimation, PRB offset, CSI-RS density configuration index,etc.).

At 1220, a set of REs for reduced density CSI-RS can be determined basedon the one or more configuration parameters.

At 1230, reduced density CSI-RS can be received via the determined setof REs.

At 1240, one or more CSI parameters can be measured based on thereceived reduced density CSI-RS.

Additionally or alternatively, method 1200 can include one or more otheracts described herein in connection with system 400.

Referring to FIG. 13, illustrated is a flow diagram of an example method1300 employable at a BS that facilitates configuration for andtransmission of reduced density CSI-RS, according to various aspectsdiscussed herein. In other aspects, a machine readable medium can storeinstructions associated with method 1300 that, when executed, can causea BS to perform the acts of method 1300.

At 1310, one or more configuration messages can be transmitted that canindicate one or more configuration parameters for reduced density CSI-RS(e.g., PRB decimation, PRB offset, CSI-RS density configuration index,etc.).

At 1320, a set of REs for reduced density CSI-RS can be determined basedon the one or more configuration parameters.

At 1330, reduced density CSI-RS can be transmitted via the determinedset of REs.

Additionally or alternatively, method 1300 can include one or more otheracts described herein in connection with system 500.

A first example embodiment employable in connection with aspectsdiscussed herein can comprise a method of transmission (e.g., viacommunication circuitry 520) of reduced density CSI-RS signals (e.g.,generated by processor(s) 510), wherein the method comprises:configuration (e.g., via DCI and/or higher layer signaling generated byprocessor(s) 510, transmitted via communication circuitry 520, receivedvia transceiver circuitry 420, and processed by processor(s) 410) of‘PRB offset’ and ‘PRB decimation’ parameters for a user equipment (UE),wherein the ‘PRB decimation’ parameter determines the density of CSI-RSAPs in the frequency domain measured in PRBs, and the ‘PRB offset’parameter indicates a starting PRB index for reduced density CSI-RStransmission; measurements (e.g., by processor(s) 410) on reduceddensity CSI-RS (e.g., generated by processor(s) 510, transmitted viacommunication circuitry 520, received via transceiver circuitry 420, andprocessed by processor(s) 410) according to the configured parameters;and CSI calculation (e.g., by processor(s) 410) according to themeasurement on the reduced density CSI-RS resource elements.

In various aspects of the first example embodiment, the ‘PRB decimation’and ‘PRB offset’ can be independently indicated (e.g., via DCI and/orhigher layer signaling generated by processor(s) 510, transmitted viacommunication circuitry 520, received via transceiver circuitry 420, andprocessed by processor(s) 410).

In various aspects of the first example embodiment, the ‘PRB decimation’and ‘PRB offset’ can be jointly coded, wherein the ‘PRB decimation’ andthe ‘PRB offset’ can be indicated via a ‘CSI-RS density configurationindex’ (e.g., via DCI and/or higher layer signaling generated byprocessor(s) 510, transmitted via communication circuitry 520, receivedvia transceiver circuitry 420, and processed by processor(s) 410).

In various aspects of the first example embodiment, the reduced densityCSI-RS parameters can be indicated using DCI signaling (e.g., generatedby processor(s) 510, transmitted via communication circuitry 520,received via transceiver circuitry 420, and processed by processor(s)410).

In various aspects of the first example embodiment, the reduced densityCSI-RS parameters can be indicated using RRC signaling (e.g., generatedby processor(s) 510, transmitted via communication circuitry 520,received via transceiver circuitry 420, and processed by processor(s)410).

In various aspects of the first example embodiment employing independentindication of the reduced density CSI-RS parameters, the reduced densityCSI-RS parameters can be indicated using RRC and DCI signaling, whereinthe ‘PRB decimation’ can be indicated via RRC (e.g., generated byprocessor(s) 510, transmitted via communication circuitry 520, receivedvia transceiver circuitry 420, and processed by processor(s) 410) andthe ‘PRB offset’ can be indicated via DCI (e.g., generated byprocessor(s) 510, transmitted via communication circuitry 520, receivedvia transceiver circuitry 420, and processed by processor(s) 410).

In various aspects of the first example embodiment, the reduced densityCSI-RS parameters can be indicated (e.g., via DCI and/or higher layersignaling generated by processor(s) 510, transmitted via communicationcircuitry 520, received via transceiver circuitry 420, and processed byprocessor(s) 410) per CSI-RS antenna port.

In various aspects of the first example embodiment, the reduced densityCSI-RS parameters can be indicated (e.g., via DCI and/or higher layersignaling generated by processor(s) 510, transmitted via communicationcircuitry 520, received via transceiver circuitry 420, and processed byprocessor(s) 410) per CSI-RS antenna port group. In various suchaspects, a first CSI-RS AP group comprises a first half of CSI-RSantenna ports and a second CSI-RS AP group comprises a second half ofCSI-RS antenna ports.

In various aspects of the first example embodiment, the reduced densityCSI-RS parameters can be indicated (e.g., via DCI and/or higher layersignaling generated by processor(s) 510, transmitted via communicationcircuitry 520, received via transceiver circuitry 420, and processed byprocessor(s) 410) per CSI-RS resource configuration, which can supportdifferent overhead reduction for non-zero power CSI-RS resourceaggregations using two or more CSI-RS resource configurations.

In various aspects of the first example embodiment, physical downlinkshared channel (PDSCH) mapping (e.g., by processor(s) 510) can be basedon assuming a non-reduced density CSI-RS, regardless of the reduceddensity CSI-RS configuration.

In various aspects of the first example embodiment, collision of CSI-RSwith paging messages (e.g., in the primary cell in subframes/slotsconfigured for transmission of paging messages in the primary cell forany UE with the cell-specific paging configuration) and broadcastmessages (e.g., transmitted SIBs (System Information Blocks) such asSystemInformationBlockType1) can be based on assuming a non-reduceddensity CSI-RS regardless of the reduced density CSI-RS configuration.

In various aspects of the first example embodiment, antenna ports ofCSI-RS can be renumbered (e.g., by processor(s) 410 and/or processor(s)510) prior to CSI calculation, wherein the renumbering of antenna portscan ensure that the same beam corresponding to different polarizationsis transmitted (e.g., by communication circuitry 520) on the sameresource element pair (CDM (Code Division Multiplexing) group), asmapped by processor(s) 510. In various such aspects, the antenna portrenumbering (e.g., by processor(s) 410 and/or processor(s) 510) can beaccording to equation (1), above.

Examples herein can include subject matter such as a method, means forperforming acts or blocks of the method, at least one machine-readablemedium including executable instructions that, when performed by amachine (e.g., a processor with memory, an application-specificintegrated circuit (ASIC), a field programmable gate array (FPGA), orthe like) cause the machine to perform acts of the method or of anapparatus or system for concurrent communication using multiplecommunication technologies according to embodiments and examplesdescribed.

Example 1 is an apparatus configured to be employed in a UE (UserEquipment), comprising: a memory interface; and processing circuitryconfigured to: process one or more configuration messages that compriseone or more configuration parameters for one or more CSI (Channel StateInformation)-RS (Reference Signal) APs (Antenna Ports) of a reduceddensity CSI-RS, wherein the one or more configuration parametersindicate a PRB (Physical Resource Block) decimation and a PRB offset;determine a set of REs (Resource Elements) for the one or more CSI-RSAPs of the reduced density CSI-RS based on the one or more configurationparameters; measure the reduced density CSI-RS from the set of REs todetermine one or more CSI parameters; and send the PRB decimation andthe PRB offset to a memory via the memory interface.

Example 2 comprises the subject matter of any variation of any ofexample(s) 1, wherein the one or more configuration parameters comprisesa single configuration parameter that indicates the PRB decimation andthe PRB offset.

Example 3 comprises the subject matter of any variation of any ofexample(s) 1, wherein the one or more configuration parameters comprisethe PRB decimation and the PRB offset.

Example 4 comprises the subject matter of any variation of any ofexample(s) 3, wherein the one or more configuration messages comprise aRRC (Radio Resource Control) message that comprises the PRB decimationand a DCI (Downlink Control Information) message that comprises the PRBoffset.

Example 5 comprises the subject matter of any variation of any ofexample(s) 1-3, wherein the one or more configuration messages comprisesa RRC (Radio Resource Control) message.

Example 6 comprises the subject matter of any variation of any ofexample(s) 1-3, wherein the one or more configuration messages comprisesa DCI (Downlink Control Information) message.

Example 7 comprises the subject matter of any variation of any ofexample(s) 1-3, wherein the one or more CSI-RS APs comprise a singleCSI-RS AP.

Example 8 comprises the subject matter of any variation of any ofexample(s) 1-3, wherein the one or more CSI-RS APs comprise two or moreCSI-RS APs in a CSI-RS group.

Example 9 comprises the subject matter of any variation of any ofexample(s) 8, wherein the two or more CSI-RS APs in the CSI-RS groupcomprise a first half of configured CSI-RS APs for the UE or a secondhalf of configured CSI-RS APs for the UE.

Example 10 comprises the subject matter of any variation of any ofexample(s) 1-3, wherein the one or more CSI-RS APs comprise each CSI-RSAP of a CSI-RS resource configuration.

Example 11 comprises the subject matter of any variation of any ofexample(s) 1-6, wherein the one or more CSI-RS APs comprise a singleCSI-RS AP.

Example 12 comprises the subject matter of any variation of any ofexample(s) 1-6, wherein the one or more CSI-RS APs comprise two or moreCSI-RS APs in a CSI-RS group.

Example 13 comprises the subject matter of any variation of any ofexample(s) 1-6, wherein the one or more CSI-RS APs comprise each CSI-RSAP of a CSI-RS resource configuration.

Example 14 is an apparatus configured to be employed in a gNB (nextGeneration Node B), comprising: a memory interface; and processingcircuitry configured to: generate one or more configuration messagesthat comprise one or more configuration parameters for one or more CSI(Channel State Information)-RS (Reference Signal) APs (Antenna Ports) ofa reduced density CSI-RS, wherein the one or more configurationparameters indicate a PRB (Physical Resource Block) decimation and a PRBoffset; determine a set of REs (Resource Elements) for the one or moreCSI-RS APs of the reduced density CSI-RS based on the one or moreconfiguration parameters; map the reduced density CSI-RS for the one ormore CSI-RS APs to the determined set of REs; and send the PRBdecimation and the PRB offset to a memory via the memory interface.

Example 15 comprises the subject matter of any variation of any ofexample(s) 14, wherein the one or more configuration parameterscomprises a single configuration parameter that indicates the PRBdecimation and the PRB offset.

Example 16 comprises the subject matter of any variation of any ofexample(s) 14, wherein the one or more configuration parameters comprisethe PRB decimation and the PRB offset.

Example 17 comprises the subject matter of any variation of any ofexample(s) 16, wherein the one or more configuration messages comprise aRRC (Radio Resource Control) message that comprises the PRB decimationand a DCI (Downlink Control Information) message that comprises the PRBoffset.

Example 18 comprises the subject matter of any variation of any ofexample(s) 14-16, wherein the one or more configuration messagescomprises a RRC (Radio Resource Control) message.

Example 19 comprises the subject matter of any variation of any ofexample(s) 14-16, wherein the one or more configuration messagescomprises a DCI (Downlink Control Information) message.

Example 20 comprises the subject matter of any variation of any ofexample(s) 14-16, wherein the one or more CSI-RS APs comprise a singleCSI-RS AP.

Example 21 comprises the subject matter of any variation of any ofexample(s) 14-16, wherein the one or more CSI-RS APs comprise two ormore CSI-RS APs in a CSI-RS group.

Example 22 comprises the subject matter of any variation of any ofexample(s) 21, wherein the two or more CSI-RS APs in the CSI-RS groupcomprise a first half of configured CSI-RS APs for the UE or a secondhalf of configured CSI-RS APs for the UE.

Example 23 comprises the subject matter of any variation of any ofexample(s) 14-16, wherein the one or more CSI-RS APs comprise eachCSI-RS AP of a CSI-RS resource configuration.

Example 24 comprises the subject matter of any variation of any ofexample(s) 14-16, wherein the processing circuitry is further configuredto map PDSCH (Physical Downlink Shared Channel) around the reduceddensity CSI-RS based on an assumption of a non-reduced density CSI-RScorresponding to the reduced density CSI-RS.

Example 25 comprises the subject matter of any variation of any ofexample(s) 14-16, wherein the processing circuitry is further configuredto perform collision handling between the reduced density CSI-RS and atleast one of paging messages or broadcast messages based on anassumption of a non-reduced density CSI-RS corresponding to the reduceddensity CSI-RS.

Example 26 comprises the subject matter of any variation of any ofexample(s) 14-16, wherein the processing circuitry is further configuredto renumber the one or more CSI-RS APs such that the processingcircuitry is configured to map the reduced density CSI-RS for eachCSI-RS AP to a first RE of an associated RE pair of an associated CDM(Code Division Multiplexing) group and to map, to a second RE of theassociated RE pair of the associated CDM group, the reduced densityCSI-RS for an additional CSI-RS AP, wherein that CSI-RS AP and theadditional CSI-RS AP are both associated with a common beam, whereinthat CSI-RS is associated with a first polarization of the common beamand the additional CSI-RS AP is associated with a distinct secondpolarization of the common beam.

Example 27 comprises the subject matter of any variation of any ofexample(s) 14-17, wherein the processing circuitry is further configuredto perform collision handling between the reduced density CSI-RS and atleast one of paging messages or broadcast messages based on anassumption of a non-reduced density CSI-RS corresponding to the reduceddensity CSI-RS.

Example 28 comprises the subject matter of any variation of any ofexample(s) 14-18, wherein the processing circuitry is further configuredto renumber the one or more CSI-RS APs such that the processingcircuitry is configured to map the reduced density CSI-RS for eachCSI-RS AP to a first RE of an associated RE pair of an associated CDM(Code Division Multiplexing) group and to map, to a second RE of theassociated RE pair of the associated CDM group, the reduced densityCSI-RS for an additional CSI-RS AP, wherein that CSI-RS AP and theadditional CSI-RS AP are both associated with a common beam, whereinthat CSI-RS is associated with a first polarization of the common beamand the additional CSI-RS AP is associated with a distinct secondpolarization of the common beam.

Example 29 is a machine readable medium comprising instructions that,when executed, cause a User Equipment (UE) to: receive one or moreconfiguration messages that comprise one or more configurationparameters for one or more CSI (Channel State Information)-RS (ReferenceSignal) APs (Antenna Ports) of a reduced density CSI-RS, wherein the oneor more configuration parameters indicate a PRB (Physical ResourceBlock) decimation and a PRB offset; determine a set of REs (ResourceElements) for the one or more CSI-RS APs of the reduced density CSI-RSbased on the one or more configuration parameters; receive the reduceddensity CSI-RS from the set of REs; and measure the reduced densityCSI-RS to determine one or more CSI parameters.

Example 30 comprises the subject matter of any variation of any ofexample(s) 29, wherein the one or more configuration parameterscomprises a single configuration parameter that indicates the PRBdecimation and the PRB offset.

Example 31 comprises the subject matter of any variation of any ofexample(s) 29, wherein the one or more configuration parameters comprisethe PRB decimation and the PRB offset.

Example 32 is a machine readable medium comprising instructions that,when executed, cause a next Generation Node B (gNB) to: transmit one ormore configuration messages that comprise one or more configurationparameters for one or more CSI (Channel State Information)-RS (ReferenceSignal) APs (Antenna Ports) of a reduced density CSI-RS, wherein the oneor more configuration parameters indicate a PRB (Physical ResourceBlock) decimation and a PRB offset; determine a set of REs (ResourceElements) for the one or more CSI-RS APs of the reduced density CSI-RSbased on the one or more configuration parameters; and transmit thereduced density CSI-RS for the one or more CSI-RS APs via the determinedset of REs.

Example 33 comprises the subject matter of any variation of any ofexample(s) 32, wherein the one or more configuration parameterscomprises a single configuration parameter that indicates the PRBdecimation and the PRB offset.

Example 34 comprises the subject matter of any variation of any ofexample(s) 32, wherein the one or more configuration parameters comprisethe PRB decimation and the PRB offset.

Example 35 comprises the subject matter of any variation of any ofexample(s) 32-34, wherein the instructions, when executed, further causethe gNB to: renumber the one or more CSI-RS APs; map the reduced densityCSI-RS for each CSI-RS AP to a first RE of an associated RE pair of anassociated CDM (Code Division Multiplexing) group and map, to a secondRE of the associated RE pair of the associated CDM group, the reduceddensity CSI-RS for an additional CSI-RS AP, wherein that CSI-RS AP andthe additional CSI-RS AP are both associated with a common beam, whereinthat CSI-RS is associated with a first polarization of the common beamand the additional CSI-RS AP is associated with a distinct secondpolarization of the common beam.

Example 36 is an apparatus configured to be employed in a UE (UserEquipment), comprising: means for receiving one or more configurationmessages that comprise one or more configuration parameters for one ormore CSI (Channel State Information)-RS (Reference Signal) APs (AntennaPorts) of a reduced density CSI-RS, wherein the one or moreconfiguration parameters indicate a PRB (Physical Resource Block)decimation and a PRB offset; means for determining a set of REs(Resource Elements) for the one or more CSI-RS APs of the reduceddensity CSI-RS based on the one or more configuration parameters; meansfor receiving the reduced density CSI-RS from the set of REs; and meansfor measuring the reduced density CSI-RS to determine one or more CSIparameters.

Example 37 comprises the subject matter of any variation of any ofexample(s) 36, wherein the one or more configuration parameterscomprises a single configuration parameter that indicates the PRBdecimation and the PRB offset.

Example 38 comprises the subject matter of any variation of any ofexample(s) 36, wherein the one or more configuration parameters comprisethe PRB decimation and the PRB offset.

Example 39 is an apparatus configured to be employed in a gNB (nextGeneration Node B), comprising: means for transmitting one or moreconfiguration messages that comprise one or more configurationparameters for one or more CSI (Channel State Information)-RS (ReferenceSignal) APs (Antenna Ports) of a reduced density CSI-RS, wherein the oneor more configuration parameters indicate a PRB (Physical ResourceBlock) decimation and a PRB offset; means for determining a set of REs(Resource Elements) for the one or more CSI-RS APs of the reduceddensity CSI-RS based on the one or more configuration parameters; andmeans for transmitting the reduced density CSI-RS for the one or moreCSI-RS APs via the determined set of REs.

Example 40 comprises the subject matter of any variation of any ofexample(s) 39, wherein the one or more configuration parameterscomprises a single configuration parameter that indicates the PRBdecimation and the PRB offset.

Example 41 comprises the subject matter of any variation of any ofexample(s) 39, wherein the one or more configuration parameters comprisethe PRB decimation and the PRB offset.

Example 42 comprises the subject matter of any variation of any ofexample(s) 39-41, further comprising: means for renumbering the one ormore CSI-RS APs; means for mapping the reduced density CSI-RS for eachCSI-RS AP to a first RE of an associated RE pair of an associated CDM(Code Division Multiplexing) group and mapping, to a second RE of theassociated RE pair of the associated CDM group, the reduced densityCSI-RS for an additional CSI-RS AP, wherein that CSI-RS AP and theadditional CSI-RS AP are both associated with a common beam, whereinthat CSI-RS is associated with a first polarization of the common beamand the additional CSI-RS AP is associated with a distinct secondpolarization of the common beam.

Example 43 comprises an apparatus comprising means for executing any ofthe described operations of examples 1-42.

Example 44 comprises a machine readable medium that stores instructionsfor execution by a processor to perform any of the described operationsof examples 1-42.

Example 45 comprises an apparatus comprising: a memory interface; andprocessing circuitry configured to: perform any of the describedoperations of examples 1-42.

The above description of illustrated embodiments of the subjectdisclosure, including what is described in the Abstract, is not intendedto be exhaustive or to limit the disclosed embodiments to the preciseforms disclosed. While specific embodiments and examples are describedherein for illustrative purposes, various modifications are possiblethat are considered within the scope of such embodiments and examples,as those skilled in the relevant art can recognize.

In this regard, while the disclosed subject matter has been described inconnection with various embodiments and corresponding Figures, whereapplicable, it is to be understood that other similar embodiments can beused or modifications and additions can be made to the describedembodiments for performing the same, similar, alternative, or substitutefunction of the disclosed subject matter without deviating therefrom.Therefore, the disclosed subject matter should not be limited to anysingle embodiment described herein, but rather should be construed inbreadth and scope in accordance with the appended claims below.

In particular regard to the various functions performed by the abovedescribed components or structures (assemblies, devices, circuits,systems, etc.), the terms (including a reference to a “means”) used todescribe such components are intended to correspond, unless otherwiseindicated, to any component or structure which performs the specifiedfunction of the described component (e.g., that is functionallyequivalent), even though not structurally equivalent to the disclosedstructure which performs the function in the herein illustratedexemplary implementations. In addition, while a particular feature mayhave been disclosed with respect to only one of several implementations,such feature may be combined with one or more other features of theother implementations as may be desired and advantageous for any givenor particular application.

What is claimed is:
 1. An apparatus configured to be employed for a UE(User Equipment), comprising: a memory interface; and processingcircuitry configured to: receive and process a configuration messagethat comprises one or more configuration parameters for one or more CSI(Channel State Information)-RS (Reference Signal) APs (Antenna Ports) ofa configurable density CSI-RS, the one or more configuration parametersindicating a density of CSI-RS resource per Physical Resource Block(PRB) per CSI-RS AP and a PRB offset; determine a set of REs (ResourceElements) for the one or more CSI-RS APs of the configurable densityCSI-RS based on the one or more configuration parameters; and performmeasurements on the configurable density CSI-RS from the set of REs todetermine one or more CSI parameters; wherein the one or moreconfiguration parameters are provided per CSI-RS resource configuration.2. The apparatus of claim 1, wherein the PRB offset indicates one PRBoffset on even PRBs or another PRB offset on odd PRBs, if the density ofCSI-RS resource is ½ per PRB per CSI-RS AP.
 3. The apparatus of claim 1,wherein the density of CSI-RS resource and the PRB offset are indicatedseparately by the one or more configuration parameters.
 4. The apparatusof claim 1, wherein the one or more CSI-RS APs comprise two or moreCSI-RS APs in a CSI-RS group; and wherein the two or more CSI-RS APs inthe CSI-RS group comprise a first half of configured CSI-RS APs for theUE or a second half of configured CSI-RS APs for the UE.
 5. Theapparatus of claim 1, wherein the one or more CSI-RS APs comprise eachCSI-RS AP of a CSI-RS resource configuration.
 6. The apparatus of claim1, wherein the PRB offset indicates an offset number of PRBs from areference PRB.
 7. An apparatus configured to be employed for a basestation, comprising: a memory interface; and processing circuitryconfigured to: generate a configuration message that comprises one ormore configuration parameters for one or more CSI (Channel StateInformation)-RS (Reference Signal) APs (Antenna Ports) of a configurabledensity CSI-RS, wherein the one or more configuration parameterscomprise indications of a density of CSI-RS resource per PhysicalResource Block (PRB) per CSI-RS AP and a PRB offset; determine a set ofREs (Resource Elements) for the one or more CSI-RS APs of theconfigurable density CSI-RS based on the one or more configurationparameters; and map the configurable density CSI-RS for the one or moreCSI-RS APs to the determined set of REs; wherein the one or moreconfiguration parameters are provided per CSI-RS resource configuration.8. The apparatus of claim 7, wherein the PRB offset indicates one PRBoffset on even PRBs or another PRB offset on odd PRBs, if the density ofCSI-RS resource is ½ per PRB per CSI-RS AP.
 9. The apparatus of claim 7,wherein the configuration message is a RRC (Radio Resource Control)message.
 10. The apparatus of claim 7, wherein the one or more CSI-RSAPs comprise a single CSI-RS AP.
 11. The apparatus of claim 7, whereinthe one or more CSI-RS APs comprise two or more CSI-RS APs in a CSI-RSgroup; and wherein the two or more CSI-RS APs in the CSI-RS groupcomprise a first half of configured CSI-RS APs or a second half ofconfigured CSI-RS APs.
 12. The apparatus of claim 7, wherein the one ormore CSI-RS APs comprise each CSI-RS AP of a CSI-RS resourceconfiguration.
 13. The apparatus of claim 7, wherein the processingcircuitry is further configured to perform collision handling betweenthe configurable density CSI-RS and at least one of paging messages orbroadcast messages based on an assumption of a non-configurable densityCSI-RS corresponding to the configurable density CSI-RS.
 14. Theapparatus of claim 7, wherein the processing circuitry is furtherconfigured to renumber the one or more CSI-RS APs such that theprocessing circuitry is configured to map the configurable densityCSI-RS for one CSI-RS AP to a first RE of an associated RE pair of anassociated CDM (Code Division Multiplexing) group and to map, to asecond RE of the associated RE pair of the associated CDM group, theconfigurable density CSI-RS for an additional CSI-RS AP, wherein thatCSI-RS AP and the additional CSI-RS AP are associated with a commonbeam, wherein that CSI-RS is associated with a first polarization of thecommon beam and the additional CSI-RS AP is associated with a distinctsecond polarization of the common beam.
 15. The apparatus of claim 7,wherein the PRB offset indicates an offset number of PRBs from areference PRB.
 16. A non-transitory machine readable medium comprisinginstructions that, when executed, cause a User Equipment (UE) to:receive a configuration message that comprises one or more configurationparameters for one or more CSI (Channel State Information)-RS (ReferenceSignal) APs (Antenna Ports) of a configurable density CSI-RS, whereinthe configuration message comprises indications of a density of CSI-RSresource per Physical Resource Block (PRB) per CSI-RS AP and a PRBoffset; determine a set of REs (Resource Elements) for the one or moreCSI-RS APs of the configurable density CSI-RS based on the one or moreconfiguration parameters; receive the configurable density CSI-RS fromthe set of REs; and measure the configurable density CSI-RS to determineone or more CSI parameters; wherein the one or more configurationparameters are provided per CSI-RS resource configuration.
 17. Thenon-transitory machine readable medium of claim 16, wherein the PRBoffset indicates one PRB offset on even PRBs or another PRB offset onodd PRBs, if the density of CSI-RS resource is ½ per PRB per CSI-RS AP.18. A non-transitory machine readable medium comprising instructionsthat, when executed, cause a base station to: transmit one or moreconfiguration messages that comprise one or more configurationparameters for one or more CSI (Channel State Information)-RS (ReferenceSignal) APs (Antenna Ports) of a configurable density CSI-RS, whereinthe one or more configuration parameters indicate a density of CSI-RSresource per Physical Resource Block (PRB) per CSI-RS AP and a PRBoffset; determine a set of REs (Resource Elements) for the one or moreCSI-RS APs of the configurable density CSI-RS based on the one or moreconfiguration parameters; and transmit the configurable density CSI-RSfor the one or more CSI-RS APs via the determined set of REs; andwherein the one or more configuration parameters are provided per CSI-RSresource configuration.
 19. The non-transitory machine readable mediumof claim 18, wherein the PRB offset indicates one PRB offset on evenPRBs or another PRB offset on odd PRBs, if the density of CSI-RSresource is ½ per PRB per CSI-RS AP.
 20. The non-transitory machinereadable medium of claim 18, wherein the density of CSI-RS resource andthe PRB offset are indicated separately by the one or more configurationparameters.